9.3.3.12 Distance The track should be located as far from
sensitive structures as practicable within the limits of the
right-of-way. Where wide rights-of-way exist, some latitude in
locating the track may exist. A shift of as little as 10 ft [3
m] away from a sensitive structure may produce a beneficial
reduction of vibration for receivers bordering the right-of-way.
Sensitive receivers located within 50 ft [15 m] of the track
centerline are particularly in danger of being impacted by
ground vibration from transit operations. However, ground
vibration and ground-borne noise impacts have occurred at
sensitive receivers at significantly greater distances.
4) Highway Grade Crossings Grade crossing warning: based on
railroad signaling technology, gates and flashers generally
eliminate any need for the LRV operator to slow down to
determine if a grade crossing is clear. Grade crossing
traffic control based on flashing lights only or even
traffic signals only have been employed, but flashers with
gates are generally recognized as the most effective type of
crossing warning system. Crossing warning indicators are
provided ahead of the highway grade crossing to inform the
train operator as to the operational status of the highway
crossing equipment. 5) Yard and Shop Operational rules and
small turnouts generally restrict train operations in yards
to low speeds, typically 5 to 10 miles per hour. Busy
switches are normally power operated; infrequently used
switches are often hand thrown. Signals or indicators are
provided where required and can be either integral with or
external to the switch machine. Signal system architecture
for a yard can be either vital or non-vital design and
include track circuits.
10.2.10.1 General Highway crossing warning systems provide
indications to motorists that a light rail vehicle is
approaching the crossing. Such systems are commonly but
erroneously called crossing “protection” systems. That term
is incorrect as there is no way to protect the train from a
motor vehicle whose operator elects to ignore the signals
and no way to protect the motorist from the consequences of
his/her failure to comply with the signals provided. What
the signals can do is warn the operator of a motor vehicle
on an intersecting path that a train is approaching.
Currently, there is no effective way to advise an LRV
operator that motor vehicles are approaching a crossing,
making it highly desirable to keep the “sight triangles” at
all four quadrants clear of obstructions such as buildings
and vegetation. The most common configuration for highway
crossing warning systems is conventional flashing light
signals, either with or without gates, such as those
commonly used on freight railroad grade crossings. In
determining the type and configuration of the highway
crossing warning system, consideration should be given to
LRV operations, type of track circuit, roadway layout and
posted speeds, traffic signal(s) location, right-of-way, and
clearances. The challenge of fail-safe crossing warning
systems is to separate the LRV and highway traffic without
closing the crossing to motor vehicle traffic for extended
periods of time. The Federal Highway Administration’s Manual
of Uniform Traffic Control Devices (MUTCD) now includes
recommendations for at-grade crossings of LRT tracks. These
requirements are included in Part 8 of the MUTCD (2009
edition), which can be downloaded from the FHWA’s website.
In some cases, crossing warning systems will include
specific signs and warning signals for pedestrians. The
track designer needs to coordinate the layout of the
crossing surface and the approach pavements so that
pedestrians are directed along paths where they can clearly
see warning devices. In addition to the requirements
currently in the MUTCD, there have been numerous
experimental installations of barriers and crossing warning
devices to promote the safety of both pedestrians and
motorists and, by extension, the operators and passengers of
the rail vehicles. One example is active signage that
flashes to indicate a “Second Train Coming” from the
opposite direction of the one that initially activated the
warning system. This issue is dynamic and LRT design teams
are encouraged to consult recent trade publications and
published papers for state-of-the-art information. Crossing
warning installations should be interconnected with any
traffic signals located within 200 feet [60 meters] of the
highway grade crossing. Additional advance warning of
approaching LRVs, i.e., more time than required at an
ordinary crossing, may be required for proper operation of
the traffic signals so as to “flush” certain legs of the
intersection prior to train arrival. An on-site diagnostic
team meeting is usually required at an early date to discuss
all of the implications of the warning system being
proposed.